Grinder pumps are often used in low pressure systems for pumping wastewater such as sewage. A grinder pump is typically disposed in a wastewater tank in which the grinder pump includes a motor for driving a grinder mechanism for cutting or grinding solids or semisolid matter in the wastewater and a pump for pumping the processed wastewater. Grinding solids and/or semisolid matter in the wastewater allows the resulting particulate effluent to be transferred using a pump through relatively small diameter pipes without clogging.
Conventional grinder pump assemblies typically have a cutting mechanism that employs a rotating cutting wheel within a stationary ring. The stationary ring has a large number of cutting surfaces oriented generally axially or perpendicular to the direction of rotation. As shown in FIGS. 1 and 2, a typical prior art rotating cutting wheel 10 has a disc-shaped base 12 and separately attachable elongated cutting elements 20. These cutting elements have sharp cutting edges oriented axially or near axially as well. The cutter wheel's outside diameter is nearly equivalent in dimension to the stationary ring's inside diameter assuring the clearance between rotating and stationary cutting edges is kept small to improve cutting efficiency. The cutting elements are typically produced from a harder, more durable material to withstand the wear of cutting. Since suitable cutting materials will tend to be more expensive, the overall cutting wheel will oftentimes be made from an inexpensive material such as cast iron with the more exotic cutting material such as stainless steel formed into the cutting elements and mounted to the cutting wheel. The elongated cutting elements on the rotating wheel agitates the wastewater in the tank during operation. This agitation keeps the solids in suspension during pumping cycles.
There is a need for improved grinder pumps, and particularly, cutting wheels for grinder pumps.